Isolation and purification of human blood plasma proteins able to form potassium channels in artificial bilayer lipid membrane

摘要

A protein fraction able to induce K~+-selective transport across a bilayer lipid membrane was isolated from human blood plasma with the use of the detergent- and proteolytic enzyme-free method developed in our laboratory. After addition of the studied sample to the artificial membrane in the presence of 100 mM KCl, a discrete current change was observed. No channel activity was recorded in the presence of calcium and sodium ions. Channel-forming activity of the fraction was observed only in the presence of K~+. Using a threefold gradient of KCl in the presence of studied proteins, a potassium-selective potential balanced by voltage of -29 mV was registered. This value is very close to the theoretical Nernst potential in this case. This means that the examined ion channel is cation-selective. According to the data obtained with MS-MALDI-TOF/TOF and NCBI database, three protein components were identified in the isolated sample.